Field of the Invention
The present invention generally relates to a method of atomic layer etching (ALE), particularly to a method of ALE using a functional group-containing fluorocarbon etchant.
Description of the Related Art
Atomic layer etching (ALE) is cyclic, atomic layer-level etching using an etchant gas adsorbed on a target film and reacted with excited reaction species, as disclosed in Japanese Patent Laid-open Publication No. 2013-235912 and No. 2014-522104. As compared with conventional etching technology, ALE can perform precise, atomic layer-level continuous etching on a sub-nanometer order to form fine, narrow convex-concave patterns and may be suitable for e.g., double-patterning processes. As an etchant gas, Cl2, HCl, CHF3, CH2F2, CH3F, H2, BCL3, SiCl4, Br2, HBr, NF3, CF4, C2F6, C4F8, SF6, O2, SO2, COS, etc. are known. However, it is revealed that in-plane uniformity of etching of a film on a substrate by ALE is not satisfactory when etching an oxide or nitride mineral film such as silicon oxide or nitride film.
Any discussion of problems and solutions in relation to the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made.